1. Field of the Invention
The present invention relates to methods for reproducing digital information, in particular digital audio from devices provided with hard disk drives, and also to digital information recording or reproducing devices.
2. Description of the Related Art
An example of such devices for recording or reproducing digital information is shown in the block diagram of FIG. 4 (see JP H8-195031A).
This is a device for storing digital audio signals transferred either from a CD player and the like via a terminal (19), or from a personal computer (5) (hereinafter, abbreviated as “PC”). Transferring the audio signals from the PC (5) means that, for example, audio signals in a compressed format that have been downloaded from a music server to the PC (5) over the Internet are transferred.
The signals input from the terminal (19) are encoded and compressed by an encoder (6), and stored in a hard disk drive (2) (hereinafter, abbreviated as “HDD”). Usually, audio signals transferred from the PC (5) are already compressed with a format such as MP3 or ATRAC, and do not have to be compressed with the encoder (6). The operation of the HDD (2) is controlled by a control circuit (4), to which operation signals from the user are input.
The control circuit (4) is connected to a memory (3) made up of an SDRAM, and the signals stored in the HDD (2) are also stored in the memory (3). “SDRAM” refers to a DRAM (volatile RAM) that operates synchronously with a clock signal, and an internal clock signal in the control circuit (4) is used as the clock signal. The reason why the device is provided with the memory (3) will be described later.
Signals to be stored in the HDD (2) and the memory (3) are expanded and decoded by a decoder (60), and thereafter output. As shown in FIG. 5, the HDD (2) is provided with a hard disk (20) that is rotated by a spindle motor (M) and a head arm (22) facing the hard disk (20), and a magnetic head (21) is disposed at the tip on the back side of the head arm (22). The HDD (2) has a known structure in which signals are recorded or reproduced by rotating the hard disk (20) to float the magnetic head (21) slightly.
Some of such devices permit the user to input an instruction to reproduce tracks in a desired order to the control circuit (4) while viewing a display (40) connected to the control circuit (4). The control circuit (4) is connected to a RAM (41) and temporarily stores this track order in the RAM (41).
A reproduction procedure in such device is described with reference to the flow chart of FIG. 6. The user has previously stored a plurality of files, in which one file corresponds to one track, in the hard disk (20). When the user turns the power on and pushes a reproduction button (not shown) (S20), the control circuit (4) is activated and initializes, i.e., resets itself (S21). Then, the HDD (2) is activated (S22) and supplies current to the spindle motor (M) to rotate the hard disk (20) (S23) after checking the operation of the peripheral circuits. The control circuit (4) verifies that data are normally readable from the HDD (2) and confirms that the spindle motor (M) is steadily rotating (S24). The control circuit (4) reads initial information (e.g., the size of the stored files) from an area called a system area (not shown) on the hard disk (20) (S25), and the audio signals recorded in the hard disk (20) then become readable.
The control circuit (4) reads the order of files to be reproduced from the RAM (41) (S26) and transmits the order to the HDD (2). Then, the HDD (2) reproduces the files in that order. The reproduced signals are temporarily transferred to the memory (3) (S27), and thereafter output from the memory (3). The audio signals are decoded in the decoder (60) and then converted into analog signals by a D/A converter (61), and thereafter output (S28).
Since the device is provided with the memory (3), in the case of reproducing the same file once again with the power kept on, the reproduction can be performed quickly by reproducing the file from the memory (3) without the need of rotating the hard disk (20).
However, the conventional device has a waiting period of about several seconds to ten seconds from when the reproduction button is pushed to when reproduced sound is output, since it undergoes the above-described steps. Particularly, in the case of using a volatile memory as the memory (3), the content of the memory (3) is erased when the power is shut off. Therefore, a waiting period of about several seconds to ten seconds has been required each time the power is turned on to perform the reproduction.
In this case, the content of the memory (3) can be preserved even after the power is shut off by using a nonvolatile memory as the memory (3). Therefore, reproduction signals become readable from the memory (3) when the power is turned on again, shortening the waiting period. However, a waiting period of about several seconds to ten seconds has been still required when the audio signals are reproduced from the hard disk (20) for the first time in a state in which no reproduction signal has yet been stored in the memory (3).
Regardless of whether the memory (3) is volatile or nonvolatile, a waiting period of about several seconds to ten seconds is similarly required when the audio signals stored in the HDD (2) are reproduced from the PC (5) or the terminal (19) immediately after storage since the audio signals have not yet been stored in the memory (3).